Breast density is a measure used to describe the proportion of the different tissues that make up a woman’s breasts.
Breasts are made up of fat and breast tissue (the milk ducts and lobules, which may be called glandular tissue). Connective tissue helps hold everything place. Learn more about the anatomy and structure of the breasts.
Breast density is not a measure of how the breasts feel, but rather how the breasts look on a mammogram.
It compares the area of breast and connective tissue seen on a mammogram to the area of fat. Breast and connective tissue are denser than fat and this difference shows up on a mammogram (see images below).
These mammogram images show a range of breast density.
Some breasts are mostly fat (fatty breast) and some breasts are mostly breast and connective tissue (dense breast).
Mammograms of dense breasts are harder to read than mammograms of fatty breasts.
Learn more about breast density and mammography.
Women with high breast density are 4-5 times more likely to get breast cancer than women with low breast density [79-80].
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High breast density is common. In the U.S., 40-50 percent of women ages 40-74 have dense breasts [21-22].
Breast density varies greatly by age and weight though. Dense breasts are more common in both young and thin women [21-22]:
Medications that contain hormones can also affect breast density. For example :
At this time, health care providers do not routinely use a woman's breast density to assess her breast cancer risk. This is mainly due to the lack of a standard measure of breast density.
While a measure of breast density may be recorded on a mammography report, this measure is not used to assess risk.
However, by looking at your mammogram or the measure of breast density, your provider may conclude that you have dense breasts and may suggest other types of breast imaging.
Some states in the U.S. have laws requiring health care providers to notify (send a letter to) women found to have dense breasts on a mammogram.
Although this may seem helpful, currently there are no special recommendations or screening guidelines for women with dense breasts.
In addition, although women with dense breasts have an increased risk of breast cancer, it is not clear that lowering breast density will decrease risk.
For example, getting older and gaining weight after menopause are both related to a decrease in breast density, but are also related to an increase in breast cancer risk.
If you have any concerns about your breast density, talk with your provider.
Komen’s statement on breast density legislation
Susan G. Komen® endorses federal legislation requiring mammography centers to report breast density information to physicians and patients. Komen believes this legislation will improve the written mammography results providers send to patients. It requires the U.S. Food and Drug Administration (FDA) to consult with leading cancer organizations (including Komen) in the development of standard wording for these patient reports. The legislation also directs the U.S. Department of Health and Human Services to focus research on improving breast cancer screening methods.
At this time, there are no special recommendations or screening guidelines for women with dense breasts.
Digital mammography offers screening benefits over film mammography for women with dense breasts . Most mammography centers now use digital mammography to screen all women.
Learn about screening for women at higher risk of breast cancer.
Breast ultrasound, breast MRI and breast tomosynthesis (each in addition to mammography) are being studied to learn whether they improve detection in women with dense breasts compared to mammography alone.
More research is needed to understand the benefits and harms of using any of these imaging tests (in addition to mammography) for women with dense breasts .
Learn more about breast ultrasound, breast MRI and breast tomosynthesis.
*Please note, the information provided within Komen Perspectives articles is only current as of the date of posting. Therefore, some information may be out of date at this time.
Research Fast Facts
Questions to Ask Your Doctor about Breast Density